In spite of the relatively favorable birth outcomes among Mexican Americans in comparison to other US racial and ethnic groups, a growing body of evidence indicates that Mexican American children experience disproportionately higher rates of health problems and developmental deficiencies during their early years of life. Known as the epidemiologic paradox, the phenomenon of relatively healthy birth outcomes among Mexican Americans, in spite of high poverty rates and low levels of prenatal care utilization, has been extensively studied, but very little research on this population has been extended to early childhood health and development outcomes. Few researchers have looked beyond birth outcomes to the effects of current social risk factors that include social environment and access to adequate health care, on early childhood health and development among Mexican Americans. One important reason for this gap in knowledge has been the lack of detailed data to simultaneously consider the wide range of potential explanatory variables across time. Therefore, the overall goal of this project is to identify the factors that influence the health and development of Mexican American children from birth through age 5 and to do so in a comparative context with the non-Hispanic white and non-Hispanic black populations. A particular goal of this study is to investigate how hypothesized protective factors present during pregnancy may or may not continue to sustain the health and development of Mexican American children beyond birth. We will examine three sets of outcomes: (a) birth outcomes, (b) child health and well-child health care, and (c) child development. Although we expect that the determinants of each of the outcomes be related, the analyses will be based on relevant conceptual models applicable to each specific outcome. Our statistical analyses will also allow us to consider the interconnections between birth outcomes, health and health care, and development in the course of early childhood. We will use national-level data from the Fragile Families and Child Wellbeing Study to conduct these analyses. The Fragile Families Study is a large, nationally representative longitudinal survey of a birth cohort of approximately 4800 children, including approximately 750 Mexican Americans, with births to unmarried parents substantially over-sampled. The data are exceptionally rich in comparison to others, which have been used to study Mexican American child health and development, allowing us a unique opportunity to more fully understand the range of factors that influence child well being within this rapidly growing population.